US4720300A - Process for producing niobium metal of an ultrahigh purity - Google Patents
Process for producing niobium metal of an ultrahigh purity Download PDFInfo
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- US4720300A US4720300A US06/869,879 US86987986A US4720300A US 4720300 A US4720300 A US 4720300A US 86987986 A US86987986 A US 86987986A US 4720300 A US4720300 A US 4720300A
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- 239000010955 niobium Substances 0.000 title claims abstract description 76
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 51
- 239000002184 metal Substances 0.000 title claims abstract description 51
- 229910052758 niobium Inorganic materials 0.000 title claims abstract description 51
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 title claims abstract description 51
- 238000000034 method Methods 0.000 title claims abstract description 26
- 239000012535 impurity Substances 0.000 claims abstract description 18
- 229910052715 tantalum Inorganic materials 0.000 claims abstract description 9
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims abstract description 9
- YHBDIEWMOMLKOO-UHFFFAOYSA-I pentachloroniobium Chemical compound Cl[Nb](Cl)(Cl)(Cl)Cl YHBDIEWMOMLKOO-UHFFFAOYSA-I 0.000 claims abstract description 7
- FWIYBTVHGYLSAZ-UHFFFAOYSA-I pentaiodoniobium Chemical compound I[Nb](I)(I)(I)I FWIYBTVHGYLSAZ-UHFFFAOYSA-I 0.000 claims description 55
- 238000005979 thermal decomposition reaction Methods 0.000 claims description 20
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 7
- 239000011261 inert gas Substances 0.000 claims description 7
- 239000003795 chemical substances by application Substances 0.000 claims 1
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 description 34
- 239000011630 iodine Substances 0.000 description 34
- 229910052740 iodine Inorganic materials 0.000 description 34
- XMBWDFGMSWQBCA-UHFFFAOYSA-N hydrogen iodide Chemical compound I XMBWDFGMSWQBCA-UHFFFAOYSA-N 0.000 description 19
- 239000007789 gas Substances 0.000 description 18
- 238000006243 chemical reaction Methods 0.000 description 17
- 238000000354 decomposition reaction Methods 0.000 description 15
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 14
- 238000000746 purification Methods 0.000 description 13
- 238000010438 heat treatment Methods 0.000 description 11
- 239000012159 carrier gas Substances 0.000 description 9
- MISXNQITXACHNJ-UHFFFAOYSA-I tantalum(5+);pentaiodide Chemical compound [I-].[I-].[I-].[I-].[I-].[Ta+5] MISXNQITXACHNJ-UHFFFAOYSA-I 0.000 description 8
- 229910052786 argon Inorganic materials 0.000 description 7
- 230000006698 induction Effects 0.000 description 7
- 239000007858 starting material Substances 0.000 description 6
- 150000004694 iodide salts Chemical class 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 238000004821 distillation Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000012776 electronic material Substances 0.000 description 2
- 229910001511 metal iodide Inorganic materials 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 238000009834 vaporization Methods 0.000 description 2
- OHVLMTFVQDZYHP-UHFFFAOYSA-N 1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-2-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]ethanone Chemical compound N1N=NC=2CN(CCC=21)C(CN1CCN(CC1)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)=O OHVLMTFVQDZYHP-UHFFFAOYSA-N 0.000 description 1
- HMUNWXXNJPVALC-UHFFFAOYSA-N 1-[4-[2-(2,3-dihydro-1H-inden-2-ylamino)pyrimidin-5-yl]piperazin-1-yl]-2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethanone Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)N1CCN(CC1)C(CN1CC2=C(CC1)NN=N2)=O HMUNWXXNJPVALC-UHFFFAOYSA-N 0.000 description 1
- VZSRBBMJRBPUNF-UHFFFAOYSA-N 2-(2,3-dihydro-1H-inden-2-ylamino)-N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]pyrimidine-5-carboxamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C(=O)NCCC(N1CC2=C(CC1)NN=N2)=O VZSRBBMJRBPUNF-UHFFFAOYSA-N 0.000 description 1
- WZFUQSJFWNHZHM-UHFFFAOYSA-N 2-[4-[2-(2,3-dihydro-1H-inden-2-ylamino)pyrimidin-5-yl]piperazin-1-yl]-1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethanone Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)N1CCN(CC1)CC(=O)N1CC2=C(CC1)NN=N2 WZFUQSJFWNHZHM-UHFFFAOYSA-N 0.000 description 1
- ZSLUVFAKFWKJRC-IGMARMGPSA-N 232Th Chemical compound [232Th] ZSLUVFAKFWKJRC-IGMARMGPSA-N 0.000 description 1
- YLZOPXRUQYQQID-UHFFFAOYSA-N 3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-1-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]propan-1-one Chemical compound N1N=NC=2CN(CCC=21)CCC(=O)N1CCN(CC1)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F YLZOPXRUQYQQID-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 229910000592 Ferroniobium Inorganic materials 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 1
- 229910052776 Thorium Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000005660 chlorination reaction Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- PNDPGZBMCMUPRI-UHFFFAOYSA-N iodine Chemical compound II PNDPGZBMCMUPRI-UHFFFAOYSA-N 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- ZFGFKQDDQUAJQP-UHFFFAOYSA-N iron niobium Chemical compound [Fe].[Fe].[Nb] ZFGFKQDDQUAJQP-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 230000000153 supplemental effect Effects 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B34/00—Obtaining refractory metals
- C22B34/20—Obtaining niobium, tantalum or vanadium
- C22B34/24—Obtaining niobium or tantalum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B4/00—Electrothermal treatment of ores or metallurgical products for obtaining metals or alloys
- C22B4/005—Electrothermal treatment of ores or metallurgical products for obtaining metals or alloys using plasma jets
Definitions
- the present invention relates to a process for producing niobium metal of an ultrahigh purity. More particularly, it relates to a process for producing niobium metal of an ultrahigh purity useful for the production of electronic materials, particularly super conductive thin films.
- niobium metal by the thermal decomposition of a metal iodide
- a closed system method wherein the iodization of niobium metal and the thermal decomposition of the iodized product are conducted in the same closed container to precipitate the metal on a heated wire, or a flow method in which niobium iodide is introduced into a decomposition chamber, whereupon the metal is precipitated on a heated wire.
- the present invention provides a process for producing niobium metal of an ultrahigh purity, which comprises iodizing niobium metal or niobium chloride containing at least tantalum as an impurity, thermally reducing the iodized product, and then thermally decomposing the reduced product.
- FIG. 1 illustrates an apparatus for continuous iodization useful for the iodization reaction of the present invention.
- FIG. 3 illustrates an apparatus for the thermal decomposition.
- Niobium metal used as the starting material in the present invention contains at least tantalum, and it further contains trace amounts of other components such as iron, aluminum, silica, tungsten, zirconium, nickel, chromium, cobalt, thorium and sodium.
- niobium chloride may be employed for the iodization.
- the iodization reaction may be conducted either in a batch system or in a continuous system.
- the continuous system is preferred from the viewpoint of the productivity and economy.
- the iodization proceeds at a high rate at a temperature of 300° C. or higher. Therefore, the reaction temperature is not critical so long as it is at least 300° C. However, it is usual to employ a reaction temperature of from 400° to 600° C.
- the iodide is purified by distillation and recovered as a high purity iodide, which is then supplied to the subsequent step of the thermal reduction.
- niobium iodide is separated from iodides of the trace amount impurities by the difference in the precipitation temperatures, whereby the trace amount impurities will be reduced to a level of about 1/10.
- the thermal reduction treatment of the iodide is conducted in an inert gas atmosphere or in a hydrogen gas atmosphere or under reduced pressure at a temperature of from 200° to 600° C., preferably from 250° to 450° C.
- the iodide is introduced into the container and heated under reduced pressure or by using, as a carrier gas, an inert gas such as argon, helium or nitrogen, or a hydrogen gas.
- the lowering phenomenon of the niobium iodide starts to proceed at a temperature of 100° C.
- the lower niobium iodide starts to form at a temperature of from about 250° to about 300° C.
- the stabilization temperature of the lower niobium iodide is lower by about 50° C. than in the case where the inert gas is used.
- the thermal behavior of the higher tantalum iodide does not substantially change.
- the difference in the vapour pressures between the lower niobium iodide and the higher tantalum iodide increases, whereby the yield of the niobium iodide will be improved.
- the temperature raising rate it is usual to employ a rate of about 500° C./min taking into the yield and the purification efficiency into consideration.
- the impurities like tantalum contained in the niobium iodide will be reduced to a level of from 1/10 to 1/100, whereby the lower niobium iodide having a high purity will be recovered.
- This step is not an essential step in the present invention. However, this step is one of the useful steps to obtain niobium metal having a higher purity. This step is conducted substantially in the same manner as the iodization step for niobium metal as described above.
- This step is one of the important steps to obtain niobium metal of an ultrahigh purity in the present invention.
- this step is a step wherein the lower niobium iodide (NbI 3 ) or the higher niobium iodide (NbI 4-5 ) is thermally decomposed to obtain niobium metal having an ultrahigh purity.
- the thermal decomposition temperature is usually at least 800° C. However, it should be at least 700° C.
- There is no particular restriction as to the pressure but it is usual to employ a pressure of not higher than 10 Torr taking the decomposition efficiency and the purification efficiency into consideration.
- the heat source which may be high-frequency induction heating or infrared heating.
- the frequency for the high-frequency induction heating is preferably from a few MHz to a few tens MHz.
- the decomposition can adequately be conducted at a temperature of about 800° C. by activating the metal iodide by the generation of the low temperature plasma, and the decomposition rate can be improved remarkably i.e. from 10 to 100 times.
- the purity of niobium metal obtained by this step can be as high as at least 99.99%, and the niobium metal will be useful for electronic materials for which an ultrahigh purity is required, particularly as a starting material for super conductive thin films or alloys.
- FIG. 1 illustrates an apparatus for continuous iodization employed for the iodization reaction of the present invention.
- FIG. 2 illustrates an apparatus for the thermal reduction.
- FIG. 3 illustrates an apparatus for the thermal decomposition.
- reference numeral 1 indicates a pot for supplemental iodine designed to supplement iodine consumed as the iodides.
- Reference numeral 2 indicates an iodine reservoir, and numeral 3 indicates a closed iodine feeder (e.g. an electromagnetic feeder), designed to supply iodine in the form of powder quantitatively to an iodine vapourizer 4.
- the iodine gasified here is then sent to a reactor 6, and reacted with crude niobium metal supplied from a crude niobium metal pot 7 quantitatively and falling onto a perforated plate 5, whereby niobium iodide is formed.
- the formed niobium iodide is precipitated in a niobium iodide purification tower 9, and the purified niobium iodide is collected into a niobium iodide collecting pot 8. Unreacted iodine and iodides of impurities are led to an iodine distillation tower. The iodides of impurities are collected into a pot 10, and the purified iodine gas is led to an iodine quenching trap 12 cooled by a cooling medium.
- the iodine gas is rapidly cooled by an inert gas cooled by a condenser 13, and formed into a powder, which is again fed back to the iodine reservoir 2.
- niobium iodide having a high purity is continuously produced, and at the same time, iodine is recycled in a completely closed system.
- the degassing and dehydration are conducted by vacuuming the entire system at a level of not higher than 10 -2 Torr, by heating the system to a temperature of at least about 300° C., and by maintaining the condition for a long period of time. Then, iodine is supplied in a proper amount to the iodine vapourizer heated to a temperature higher than the boiling point of iodine, and the entire system is made under an iodine atmosphere. Further, when the respective portions reach the predetermined temperatures, crude niobium metal is supplied for iodization.
- reference numeral 21 indicates a carrier gas inlet
- numeral 22 indicates a reaction tube for the thermal reduction
- numeral 23 indicates niobium iodide.
- a proper amount of the carrier gas is introduced from the carrier gas inlet 21 into the reaction tube for the thermal reduction in which niobium iodide 23 is placed, and the thermal reduction is conducted.
- the vapourized impurities such as the higher tantalum iodide are collected by an impurity collecting trap 24.
- the purified lower niobium iodide remains in the reaction tube 22, and is recovered, whereas the iodides of impurities 25 accumulate in the impurity collecting trap 24.
- Reference numeral 26 in FIG. 2 indicates an exhaust gas line.
- reference numeral 31 indicates a purified niobium iodide gas inlet
- numeral 32 indicates a low temperature plasma
- numeral 33 indicates a high frequency induction heating coil
- numeral 34 is a seed metal
- numeral 35 indicates a gas outlet. From the inlet 31, the purified niobium iodide is introduced in the form of a gas, and decomposed in the vicinity of the seed metal 34 (most preferably niobium metal i.e. the same as the precipitating metal) heated to a high temperature by the high frequency induction heating coil 33, whereupon niobium metal deposits on the seed metal.
- the seed metal 34 most preferably niobium metal i.e. the same as the precipitating metal
- argon gas is supplied form the gas inlet 31 to generate a stabilized low temperature plasma 32 below the seed metal 34, and the purified niobium iodide gas is activated in the plasma.
- the thermal decomposition of the purified niobium iodide can be conducted at a temperature lower by about 200° C. than the conventional decomposition temperature, and yet the decomposition rate is improved by from 10 to 100 times.
- a reduced pressure of not higher than 1 to 2 Torr is sufficient when the purified niobium gas iodide and argon gas flow in the system. Unreacted iodine and liberated iodine are removed from the gas outlet 35 and then recovered for reuse.
- the ratio of bound iodine in the formed niobium iodide is shown in Table 2.
- niobium pentachloride having a particle diameter of from 10 to 100 ⁇ m obtained by the chlorination and purification of commercially available ferroniobium, was supplied (0.15 g/min) to the reaction tube in a counter current relation with HI, and HI containing 2% of I 2 was introduced at a rate of 0.7 g/min.
- the reaction zone was preliminarily heated to 150° C.
- the iodide collected at the lower portion of the reaction tube was niobium pentaiodide (NbI 5 ) comprising 12.3% of Nb, 0.4% of free iodine and 87.3% of bound iodine.
- the yield was 97%.
- Niobium pentaiodide thereby obtained was 25 g. Free iodine was 0.2%. The yield was 95%.
- NbI 5 niobium iodide
- TaI 5 tantalum iodide
- the thermal reduction was conducted for 2 hours to remove tantalum by using 100 ml/min of argon gas as the carrier gas.
- the temperature raising rate was 500° C./min.
- the Ta content (based on Nb) in the remained niobium iodide and the yield of Nb are as shown in Table 3.
- Table 9 shows the decomposition efficiency and the purification effects in the cases where the vacuum degree was differentiated at levels of atmospheric pressure, 30 Torr, 10 Torr, 4 Torr and 0.2 Torr without generating a plasma by using the same apparatus and a high frequency heating apparatus of 400 KHz.
- Nb having an ultrahigh purity of at least 99.99% by purifying crude niobium metal having a poor purity (from 99 to 99.9%) by the process of the present invention.
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Abstract
A process for producing niobium metal of an ultrahigh purity, which comprises iodizing niobium metal or niobium chloride containing at least tantalum as an impurity, thermally reducing the iodized product, and then thermally decomposing the reduced product.
Description
The present invention relates to a process for producing niobium metal of an ultrahigh purity. More particularly, it relates to a process for producing niobium metal of an ultrahigh purity useful for the production of electronic materials, particularly super conductive thin films.
Heretofore, a purity of 99.9% has been the upper limit for the purity of so-called high purity niobium metal. No process has been known which is capable of efficiently producing niobium metal having an ultrahigh purity of at least 99.99%. For a process for producing niobium metal by the thermal decomposition of a metal iodide, there has been known a closed system method wherein the iodization of niobium metal and the thermal decomposition of the iodized product are conducted in the same closed container to precipitate the metal on a heated wire, or a flow method in which niobium iodide is introduced into a decomposition chamber, whereupon the metal is precipitated on a heated wire. This flow method has an advantage that the iodide can be purified prior to the thermal decomposition. However, both of the above methods have problems such that the decomposition rate of the iodide is very slow (0.01-0.02 g/cm2.hr), and the decomposition temperature is required to be as high as at least 1000° C., whereby it is hardly possible to avoid the reaction of the precipitated metal with the material constituting the container.
Further, it has been reported that in the case of titanium metal, the decomposition rate can be improved by high-frequency heating of the metal in the form of a rod under reduced pressure so that a gaseous iodide is thermally decomposed (Research Report No. 3, 1982, Kinzoku Zairyo Gijutsu Kenkyusho, p 292-302). However, it is difficult to obtain niobium metal of an ultrahigh purity by this method. Further, the decomposition rate is not yet satisfactory, and there still remains a problem that the productivity is poor.
It is an object of the present invention to produce niobium metal of an ultrahigh purity which could not be obtained by the conventional methods. Namely, it is an object of the present invention to provide niobium metal having a purity of at least 99.99% with high production efficiency.
The present invention provides a process for producing niobium metal of an ultrahigh purity, which comprises iodizing niobium metal or niobium chloride containing at least tantalum as an impurity, thermally reducing the iodized product, and then thermally decomposing the reduced product.
Now, the present invention will be described in detail with reference to the preferred embodiments.
In the accompanying drawings,
FIG. 1 illustrates an apparatus for continuous iodization useful for the iodization reaction of the present invention.
FIG. 2 illustrates an apparatus for the thermal reduction.
FIG. 3 illustrates an apparatus for the thermal decomposition.
The process steps of the present invention may be represented by the following reaction formulas.
(1) Iodization step
Nb(Ta)+5/2I2 →Nb(Ta)I5 or
Nb(Ta)Cl5 +5HI→Nb(Ta)I5 +5HCl
(2) Thermal reduction step
Nb(Ta)I5 →NbI3 ↓(TaI5 ↑)
(3) Second iodization step
NbI3 +I2 →NbI5
(4) Thermal decomposition step
NbI5 →Nb+5/2I2 or
NbI3 →Nb+3/2I2
Now, the present invention will be described step by step in further detail.
(1) Iodization step
Niobium metal used as the starting material in the present invention, hereinafter referred to as "crude niobium metal") contains at least tantalum, and it further contains trace amounts of other components such as iron, aluminum, silica, tungsten, zirconium, nickel, chromium, cobalt, thorium and sodium. In addition to the crude niobium metal, niobium chloride may be employed for the iodization.
The iodization reaction may be conducted either in a batch system or in a continuous system. However, the continuous system is preferred from the viewpoint of the productivity and economy.
The iodization proceeds at a high rate at a temperature of 300° C. or higher. Therefore, the reaction temperature is not critical so long as it is at least 300° C. However, it is usual to employ a reaction temperature of from 400° to 600° C. After the completion of the reaction, the iodide is purified by distillation and recovered as a high purity iodide, which is then supplied to the subsequent step of the thermal reduction. In the distillation step, niobium iodide is separated from iodides of the trace amount impurities by the difference in the precipitation temperatures, whereby the trace amount impurities will be reduced to a level of about 1/10.
(2) Thermal reduction step
The thermal reduction treatment of the iodide is conducted in an inert gas atmosphere or in a hydrogen gas atmosphere or under reduced pressure at a temperature of from 200° to 600° C., preferably from 250° to 450° C. Namely, the iodide is introduced into the container and heated under reduced pressure or by using, as a carrier gas, an inert gas such as argon, helium or nitrogen, or a hydrogen gas.
With respect to the separation of niobium from the impurities like tantalum, in the case of an inert gas atmosphere, the higher niobium iodide (NbI4-5) starts to undergo a conversion to a lower homologue by the liberation of iodine at a temperature of about 200° C., and starts to form the lower niobium iodide (NbI3) at a temperature of from about 300° to about 350° C., while the higher tantalum iodide (TaI4-5) does not undergo a conversion to a lower homologue, whereby due to the substantial difference in the vapour pressures between the lower niobium iodide and the higher tantalum iodide, the impurities like tantalum will be removed from niobium. At a temperature of higher than 600° C., the lower niobium iodide starts to vapourize, and it is not preferable to employ such a high temperature for the reduction according to the present invention.
In the case where the thermal reduction is conducted in a hydrogen gas atmosphere, the lowering phenomenon of the niobium iodide starts to proceed at a temperature of 100° C., and the lower niobium iodide starts to form at a temperature of from about 250° to about 300° C. Namely, the stabilization temperature of the lower niobium iodide is lower by about 50° C. than in the case where the inert gas is used. Whereas, the thermal behavior of the higher tantalum iodide does not substantially change. Therefore, the difference in the vapour pressures between the lower niobium iodide and the higher tantalum iodide increases, whereby the yield of the niobium iodide will be improved. There is no particular restriction as to the temperature raising rate. However, it is usual to employ a rate of about 500° C./min taking into the yield and the purification efficiency into consideration.
In this step, the impurities like tantalum contained in the niobium iodide will be reduced to a level of from 1/10 to 1/100, whereby the lower niobium iodide having a high purity will be recovered.
(3) Second iodization step
This step is not an essential step in the present invention. However, this step is one of the useful steps to obtain niobium metal having a higher purity. This step is conducted substantially in the same manner as the iodization step for niobium metal as described above.
(4) Thermal decomposition step
This step is one of the important steps to obtain niobium metal of an ultrahigh purity in the present invention. Namely, this step is a step wherein the lower niobium iodide (NbI3) or the higher niobium iodide (NbI4-5) is thermally decomposed to obtain niobium metal having an ultrahigh purity. The thermal decomposition temperature is usually at least 800° C. However, it should be at least 700° C. There is no particular restriction as to the pressure, but it is usual to employ a pressure of not higher than 10 Torr taking the decomposition efficiency and the purification efficiency into consideration.
There is no particular restriction as to the heat source, which may be high-frequency induction heating or infrared heating. However, it is one of the preferred methods in the present invention that by using a high-frequency induction heating apparatus, a low temperature plasma is generated under vacuum to decompose the iodide and thereby to precipitate niobium metal of an ultrahigh purity. Here, the frequency for the high-frequency induction heating is preferably from a few MHz to a few tens MHz.
Heretofore, a temperature of at least 1000° C. has been required for the thermal decomposition. Whereas, according to the thermal decomposition by means of this high-frequency induction heating apparatus, the decomposition can adequately be conducted at a temperature of about 800° C. by activating the metal iodide by the generation of the low temperature plasma, and the decomposition rate can be improved remarkably i.e. from 10 to 100 times. Further, the purity of niobium metal obtained by this step can be as high as at least 99.99%, and the niobium metal will be useful for electronic materials for which an ultrahigh purity is required, particularly as a starting material for super conductive thin films or alloys.
Now, the present invention will be described with reference to the drawings. FIG. 1 illustrates an apparatus for continuous iodization employed for the iodization reaction of the present invention. FIG. 2 illustrates an apparatus for the thermal reduction. Likewise, FIG. 3 illustrates an apparatus for the thermal decomposition.
Referring to FIG. 1, reference numeral 1 indicates a pot for supplemental iodine designed to supplement iodine consumed as the iodides. Reference numeral 2 indicates an iodine reservoir, and numeral 3 indicates a closed iodine feeder (e.g. an electromagnetic feeder), designed to supply iodine in the form of powder quantitatively to an iodine vapourizer 4. The iodine gasified here, is then sent to a reactor 6, and reacted with crude niobium metal supplied from a crude niobium metal pot 7 quantitatively and falling onto a perforated plate 5, whereby niobium iodide is formed. The formed niobium iodide is precipitated in a niobium iodide purification tower 9, and the purified niobium iodide is collected into a niobium iodide collecting pot 8. Unreacted iodine and iodides of impurities are led to an iodine distillation tower. The iodides of impurities are collected into a pot 10, and the purified iodine gas is led to an iodine quenching trap 12 cooled by a cooling medium. Here, the iodine gas is rapidly cooled by an inert gas cooled by a condenser 13, and formed into a powder, which is again fed back to the iodine reservoir 2. Thus, niobium iodide having a high purity is continuously produced, and at the same time, iodine is recycled in a completely closed system.
Referring to the operational method more specifically, the degassing and dehydration are conducted by vacuuming the entire system at a level of not higher than 10-2 Torr, by heating the system to a temperature of at least about 300° C., and by maintaining the condition for a long period of time. Then, iodine is supplied in a proper amount to the iodine vapourizer heated to a temperature higher than the boiling point of iodine, and the entire system is made under an iodine atmosphere. Further, when the respective portions reach the predetermined temperatures, crude niobium metal is supplied for iodization.
Referring to FIG. 2, reference numeral 21 indicates a carrier gas inlet, numeral 22 indicates a reaction tube for the thermal reduction, and numeral 23 indicates niobium iodide. A proper amount of the carrier gas is introduced from the carrier gas inlet 21 into the reaction tube for the thermal reduction in which niobium iodide 23 is placed, and the thermal reduction is conducted. The vapourized impurities such as the higher tantalum iodide are collected by an impurity collecting trap 24. Thus, the purified lower niobium iodide remains in the reaction tube 22, and is recovered, whereas the iodides of impurities 25 accumulate in the impurity collecting trap 24. Reference numeral 26 in FIG. 2 indicates an exhaust gas line.
In FIG. 3, reference numeral 31 indicates a purified niobium iodide gas inlet, numeral 32 indicates a low temperature plasma, numeral 33 indicates a high frequency induction heating coil, numeral 34 is a seed metal, numeral 35 indicates a gas outlet. From the inlet 31, the purified niobium iodide is introduced in the form of a gas, and decomposed in the vicinity of the seed metal 34 (most preferably niobium metal i.e. the same as the precipitating metal) heated to a high temperature by the high frequency induction heating coil 33, whereupon niobium metal deposits on the seed metal. At the same time, argon gas is supplied form the gas inlet 31 to generate a stabilized low temperature plasma 32 below the seed metal 34, and the purified niobium iodide gas is activated in the plasma. Surprisingly, by such a method, the thermal decomposition of the purified niobium iodide can be conducted at a temperature lower by about 200° C. than the conventional decomposition temperature, and yet the decomposition rate is improved by from 10 to 100 times. For the generation of the low temperature plasma and for the decomposition, a reduced pressure of not higher than 1 to 2 Torr is sufficient when the purified niobium gas iodide and argon gas flow in the system. Unreacted iodine and liberated iodine are removed from the gas outlet 35 and then recovered for reuse.
Now, the present invention will be described in detail with reference to Examples. However, it should be understood that the present invention is by no means restricted by these specific Examples.
By using the apparatus as shown in FIG. 1, crude niobium metal was continuously iodized under the following conditions.
______________________________________
Conditions (1) (2)
______________________________________
Iodine supply rate 13 g/min 13 g/min
Niobium supply rate 1 g/min 1 g/min
Iodine vapourizer temperature
200° C.
220° C.
Iodization temperature
500° C.
550° C.
Tower top temperature of the
250° C.
180° C.
iodide purification tower
Tower top temperature of the
185° C.
190° C.
iodine purification tower
Tower bottom temperature of
200° C.
200° C.
the iodine purification
tower
Niobium iodide forming rate
6.4 g/min
7.5 g/min
______________________________________
The purification effects by the production of niobium iodide under the above conditions are shown in Table 1.
TABLE 1
______________________________________
(1) (2)
Ta Fe Al Ta Fe Al
______________________________________
Crude niobium metal
2000 20 30 2000 20 30
(ppm)
Impurities (as
180 2 5 200 3 6
calculated as niobium)
in the iodide (ppm)
______________________________________
Metal impurities other than Ta, Fe and Al were less than 1 ppm.
The ratio of bound iodine in the formed niobium iodide is shown in Table 2.
TABLE 2
______________________________________
Nb Bound iodine
Free iodine
I/Nb
(wt. %) (wt. %) (wt. %) (molar ratio)
______________________________________
(1) 12.95 87.03 0.02 4.92
(2) 12.90 87.05 0.05 4.94
______________________________________
Examples for the iodization step where niobium chloride was used as the starting material, will be given.
10 g of niobium pentachloride having a particle diameter of from 10 to 100 μm obtained by the chlorination and purification of commercially available ferroniobium, was supplied (0.15 g/min) to the reaction tube in a counter current relation with HI, and HI containing 2% of I2 was introduced at a rate of 0.7 g/min.
The reaction zone was preliminarily heated to 150° C. The iodide collected at the lower portion of the reaction tube was niobium pentaiodide (NbI5) comprising 12.3% of Nb, 0.4% of free iodine and 87.3% of bound iodine. The yield was 97%.
Niobium pentachloride as used in Example 1-2-1 was heated to 200° C., and supplied (0.15 g/min) to a horizontal type reactor by using argon gas as the carrier gas. HI gas and I2 gas (partial pressure: 100 mmHg) were supplied at a rate of 0.7 g/min. The reaction temperature was kept at 300° C.
Niobium pentaiodide thereby obtained was 25 g. Free iodine was 0.2%. The yield was 95%.
An apparatus as shown in FIG. 2 was used. 50 g of niobium iodide (NbI5) containing 0.12% by weight of tantalum iodide (TaI5) (obtained by iodizing niobium containing 2000 ppm of tantalum) was employed as the starting material iodide. The thermal reduction was conducted for 2 hours to remove tantalum by using 100 ml/min of argon gas as the carrier gas. The temperature raising rate was 500° C./min. The Ta content (based on Nb) in the remained niobium iodide and the yield of Nb are as shown in Table 3.
TABLE 3
______________________________________
Thermal reduction
Ta content (based
Yield of
temperature (°C.)
on Nb) (ppm) Nb (%)
______________________________________
250 500 87
300 50 92
350 30 83
400 10 87
450 9 85
______________________________________
The thermal reduction was conducted under the same conditions as in Example 2-1 except that 100 ml/min of hydrogen gas was used as the carrier gas. The results are shown in Table 4.
TABLE 4
______________________________________
Thermal reduction
Ta content (based
Yield of
temperature (°C.)
on Nb) (ppm) Nb (%)
______________________________________
200 800 99
250 150 98
300 10 98
350 5 97
400 4 96
______________________________________
As shown above, the yield was remarkably improved by using hydrogen gas.
Table 5 shows the results on the Ta content (based on Nb) in the remained niobium iodide and the yield of Nb in the cases where the temperature raising rate was differentiated at levels of 150° C./min, 300° C./min and 500° C./min by using the same starting material iodide as used in Examples 2-1 and 2-2 and 100 ml/min of hydrogen as the carrier gas at a thermal reduction temperature of 300° C. or 400° C. for a thermal reduction time of 2 hours.
TABLE 5
______________________________________
Thermal reduction
Temperature Ta content Yield
temperature raising rate
(based on Nb)
of Nb
(°C.)
(°C./min)
(ppm) (%)
______________________________________
300 150 35 87
300 12 94
500 10 98
400 150 32 85
300 6 91
500 4 96
______________________________________
The thermal reduction was conducted by using the same starting material iodide and the same apparatus as used in Examples 2-1 and by vacuuming the apparatus to maintain the interior under reduced pressure. The results are shown in Table 6.
TABLE 6
______________________________________
Thermal reduction
Ta content (based
Yield of
temperature (°C.)
on Nb) (ppm) Nb (%)
______________________________________
200 230 98
300 120 95
400 92 89
500 132 72
______________________________________
By using the same apparatus as used in the first iodization step, the lower niobium iodide instead of the crude niobium metal, was continuously iodized.
The conditions for the second iodization are shown below, and the quality of the niobium iodide thereby obtained is shown in Table 7.
______________________________________
Conditions
______________________________________
Iodine supply rate 13 g/min
Lower iodide supply rate
13 g/min
Second iodization temperature
500° C.
Tower top temperature of iodide
250° C.
purification tower
______________________________________
TABLE 7
______________________________________
Ta Fe Al
______________________________________
Impurities (as calculated as
30 4 7
niobium) in the lower niobium
iodide (ppm)
Impurities (as calculated as
25 2 2
niobium) in the purified
iodide (ppm)
______________________________________
By using an apparatus as shown in FIG. 3, the niobium iodide purified in the above-mentioned step was thermally decomposed. The conditions for the thermal decomposition are as shown below. The frequency of the high frequency induction heating apparatus was 4 MHz to generate a low temperature plasma. A niobium metal rod having a diameter of 10 mm and a length of 25 mm was used as a seed metal rod.
______________________________________
Conditions (1) (2)
______________________________________
Thermal decomposition
800° C.
1000° C.
temperature
Niobium iodide supply rate
60 g/Hr 60 g/Hr
Vacuum degree 2 × 10.sup.-1 Torr
2 × 10.sup.-1 Torr
Argon gas flow rate
10-20 ml/min
10-20 ml/min
______________________________________
The results of the thermal decomposition are shown in Table 8.
TABLE 8
______________________________________
Nb precipitation rate
Analytical values
(1) (2)
(ppm) 1.0 g/cm.sup.3 · Hr
4.0 g/cm.sup.3 · Hr
______________________________________
Ta 7 10
Fe <1 <1
Al <1 <1
O 10 10
H <1 <1
C 25 25
______________________________________
The total amount of other components was not higher than 1 ppm.
As described in the foregoing, the precipitation rate is remarkably improved over the conventional methods, and Nb having an ultrahigh purity of at least 99.99% was obtained.
Table 9 shows the decomposition efficiency and the purification effects in the cases where the vacuum degree was differentiated at levels of atmospheric pressure, 30 Torr, 10 Torr, 4 Torr and 0.2 Torr without generating a plasma by using the same apparatus and a high frequency heating apparatus of 400 KHz.
TABLE 9
______________________________________
Decomposition
Ta concentra-
efficiency (%)
tion (ppm)
______________________________________
Atmospheric 18 24
pressure
30 Torr 20 20
10 Torr 38 15
4 Torr 40 12
0.2 Torr 53 10
______________________________________
Working Examples will be given which show the entire process of the present invention comprising a series of the above described steps. The conditions of the respective steps are shown in Table 10. The purification states and the analytical values of the final niobium of an ultrahigh purity thereby obtained are shown in Table 11.
TABLE 10
__________________________________________________________________________
Steps Conditions for the respective steps
(1) (2)
__________________________________________________________________________
Iodization
Iodine supply rate 13 g/min
13 g/min
Niobium supply rate 1 g/min
1 g/min
Iodine vapourization temperature
200° C.
200° C.
Iodization temperature 500° C.
550° C.
Tower top temperature of iodide purification tower
250° C.
180° C.
Thermal Thermal reduction temperature
450° C.
400° C.
reduction
Carrier gas (flow rate) Ar(500 ml/min)
Ar(500 ml/min)
Temperature raising rate 500° C./min
500° C./min
Amount (niobium iodide) treated for thermal reduction
600 g 600 g
Thermal reduction time 4 Hr 4 Hr
Second Second iodization temperature
500° C.
500° C.
iodization
Iodine vapourization temperature for second iodization
200° C.
200° C.
Thermal Thermal decomposition temperature
1000° C.
1100° C.
decomposition
Niobium supply rate 69 g/Hr 60 g/Hr
Vacuum degree 2 × 10.sup.-1 Torr
2 × 10.sup.-1 Torr
Argon gas flow rate 10-20 ml/min
10-20 ml/min
__________________________________________________________________________
TABLE 11
__________________________________________________________________________
Purification results
Ta Fe Al Si W Zr Cr Mo O H C
__________________________________________________________________________
Crude niobium metal
2000
20 30 20 30 10 10
10
200
10
100
After iodization
(1)
180 2 5 8 2 5 <1 <1 -- -- --
(2)
200 3 6 12 2 8 <1 <1 -- -- --
After thermal
(1)
8 3 2 <1 <1 <1 <1 <1 -- -- --
reduction (2)
15 4 2 <1 <1 <1 <1 <1 -- -- --
After thermal
(1)
6 <1 <1 <1 <1 <1 <1 <1 15
<1 25
decomposition*
(2)
8 <1 <1 <1 <1 <1 <1 <1 15
<1 25
__________________________________________________________________________
(Analytical values are all based on Nb. (Unit: ppm))
*Analytical values for the final niobium of an ultrahigh purity.
As shown above, it is possible to obtain Nb having an ultrahigh purity of at least 99.99% by purifying crude niobium metal having a poor purity (from 99 to 99.9%) by the process of the present invention.
Claims (8)
1. A process for producing niobium metal of ultrahigh purity, which comprises:
(a) iodizing niobium metal or niobium chloride containing at least tantalum as an impurity, in the presence of an iodizing agent at a temperature of at least 300° C., thereby preparing an iodized product containing a higher niobium iodide;
(b) thermally reducing said iodized product in an inert gas atmosphere at a temperature of from 200°-600° C., or a hydrogen gas atmosphere at a temperature from 100°-300° C., thereby converting at least a portion of said higher niobium iodide to a lower niobium iodide; and
(c) thermally decomposing the higher and lower niobium iodides at a temperature of at least 700° C., thereby forming said niobium metal.
2. The process according to claim 1, wherein said iodization in step (a) is effected at a temperature of 400°-600° C.
3. The process according to claim 1, wherein the thermmal reduction of the iodized product in an inert gas atmosphere in step (b) is effected at a temperature of from 250°-450° C.
4. The process according to claim 1, wherein the thermal decomposition of step (c) is further conducted at a pressure of not more than 10 Torr.
5. The process according to claim 1, wherein the thermal decomposition is conducted by a low temperature plasma.
6. The process according to claim 1, wherein the thermal decomposition is conducted under atmospheric pressure or under reduced pressure.
7. The process according to claim 1, wherein the niobium metal of an ultrahigh purity has a purity of at least 99.99%.
8. The process according to claim 1, which further comprises iodizing the thermally reduced product between the steps of thermal reduction and thermal decomposition.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60118774A JPS61276975A (en) | 1985-06-03 | 1985-06-03 | Manufacture of extremely high purity metallic niobium |
| JP60-118774 | 1985-06-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US4720300A true US4720300A (en) | 1988-01-19 |
Family
ID=14744740
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US06/869,879 Expired - Fee Related US4720300A (en) | 1985-06-03 | 1986-06-03 | Process for producing niobium metal of an ultrahigh purity |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4720300A (en) |
| EP (1) | EP0204298B1 (en) |
| JP (1) | JPS61276975A (en) |
| BR (1) | BR8602566A (en) |
| CA (1) | CA1276072C (en) |
| DE (1) | DE3686738T2 (en) |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5188810A (en) * | 1991-06-27 | 1993-02-23 | Teledyne Industries, Inc. | Process for making niobium oxide |
| US5211921A (en) * | 1991-06-27 | 1993-05-18 | Teledyne Industries, Inc. | Process of making niobium oxide |
| US5234674A (en) * | 1991-06-27 | 1993-08-10 | Teledyne Industries, Inc. | Process for the preparation of metal carbides |
| US5284639A (en) * | 1991-06-27 | 1994-02-08 | Teledyne Industries, Inc. | Method for the preparation of niobium nitride |
| US5322548A (en) * | 1991-06-27 | 1994-06-21 | Teledyne Industries, Inc. | Recovery of niobium metal |
| US5468464A (en) * | 1991-06-27 | 1995-11-21 | Teledyne Industries, Inc. | Process for the preparation of metal hydrides |
| US6007597A (en) * | 1997-02-28 | 1999-12-28 | Teledyne Industries, Inc. | Electron-beam melt refining of ferroniobium |
| US20040216558A1 (en) * | 2003-04-25 | 2004-11-04 | Robert Mariani | Method of forming sintered valve metal material |
| WO2013006600A1 (en) * | 2011-07-05 | 2013-01-10 | Orchard Material Technology, Llc | Retrieval of high value refractory metals from alloys and mixtures |
| US9437486B2 (en) | 1998-06-29 | 2016-09-06 | Kabushiki Kaisha Toshiba | Sputtering target |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2709307C1 (en) * | 2019-03-06 | 2019-12-17 | ООО "ЭПОС-Инжиниринг" | Crystallizer for electroslag remelting |
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|---|---|---|---|---|
| US5188810A (en) * | 1991-06-27 | 1993-02-23 | Teledyne Industries, Inc. | Process for making niobium oxide |
| US5211921A (en) * | 1991-06-27 | 1993-05-18 | Teledyne Industries, Inc. | Process of making niobium oxide |
| US5234674A (en) * | 1991-06-27 | 1993-08-10 | Teledyne Industries, Inc. | Process for the preparation of metal carbides |
| US5284639A (en) * | 1991-06-27 | 1994-02-08 | Teledyne Industries, Inc. | Method for the preparation of niobium nitride |
| US5322548A (en) * | 1991-06-27 | 1994-06-21 | Teledyne Industries, Inc. | Recovery of niobium metal |
| US5468464A (en) * | 1991-06-27 | 1995-11-21 | Teledyne Industries, Inc. | Process for the preparation of metal hydrides |
| US6007597A (en) * | 1997-02-28 | 1999-12-28 | Teledyne Industries, Inc. | Electron-beam melt refining of ferroniobium |
| US9437486B2 (en) | 1998-06-29 | 2016-09-06 | Kabushiki Kaisha Toshiba | Sputtering target |
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Also Published As
| Publication number | Publication date |
|---|---|
| BR8602566A (en) | 1987-02-03 |
| EP0204298A2 (en) | 1986-12-10 |
| DE3686738D1 (en) | 1992-10-22 |
| JPS61276975A (en) | 1986-12-06 |
| DE3686738T2 (en) | 1993-01-28 |
| EP0204298B1 (en) | 1992-09-16 |
| EP0204298A3 (en) | 1989-04-19 |
| CA1276072C (en) | 1990-11-13 |
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